WO2022174364A1

WO2022174364A1 - Antenna for a wireless communication device and such a device

Info

Publication number: WO2022174364A1
Application number: PCT/CN2021/076672
Authority: WO
Inventors: Michael Kadichevitz; Doron Ezri; Avi WEITZMAN; Xin Luo; Shuguang XIAO
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-02-18
Filing date: 2021-02-18
Publication date: 2022-08-25
Anticipated expiration: 2023-08-18
Also published as: EP4197063B1; EP4197063A4; EP4197063A1

Abstract

An antenna for a wireless communication device, in particular a wireless access point is disclosed. The antenna comprises at least one radiating element configured to radiate electromagnetic radiation in response to an input signal, wherein the input signal extends over an operating frequency band, a feeding network configured to feed the input signal from an input port of the feeding network to the at least one radiating element for driving the at least one radiating element with the input signal to radiate electromagnetic radiation and a narrowband band-stop filter configured to filter the input signal. The narrowband band-stop filter comprises a conducting line resonator coupled to the feeding network, wherein the conducting line resonator is configured to filter the input signal in at least one stopband of the operating frequency band and has a length that is an integer multiple of the quarter wavelength of a stopband frequency.

Description

Antenna for a wireless communication device and such a device

TECHNICAL FIELD

The present disclosure relates to wireless communications in general. More specifically, the present disclosure relates to an antenna for a wireless communication device, in particular a wireless access point, as well as such a wireless communication device.

BACKGROUND

Modern wireless enterprise access points (herein also referred to as WiFi APs or short APs) are characterized by an increasing number of functionalities, such as two or more WiFi radios, a higher MIMO rank as well as enabling additional technologies (BT, IoT, and the like) . As a consequence, there is a trend to increase the number of antennas within an AP that may operate within the same or different operating frequency bands. This, in turn, increases the need for an efficient isolation between the different antennas allowing for a coexistence of different radios operating in different operating frequency bands. For instance, operating an AP with the recently introduced further Wi-Fi 6 GHz frequency band in parallel to the usual Wi-Fi 5 GHz frequency band requires a filter having a very steep slope over a relatively small frequency range.

BAW (bulk acoustic wave) filters have been used, but these types of filters are rather expensive and often still consume a portion of the desired operating frequency bands of an AP. Moreover, APs often operate using two 2 polarizations, namely a vertical polarization that may be based on a monopole or patch antenna and a horizontal polarization that may be based on a horizontal dipole or slot array antenna. Each of these polarizations may require different filters. The size of an antenna of an AP is usually limited by the size of the housing of the AP. Usually, high performance printed filters tend to be large in size, since they are implemented on low dielectric constant substrates. Designing a compact form-factor filter on a low dielectric constant substrate is very challenging. Moreover, most filters are based on coupled lines and therefore are plagued by parasitic radiation, which counteracts the requirement of high isolation between the different antennas of an AP. On-top-of-that, deploying two or more types of filters in an antenna is an even more challenging task as the filters may interfere with each other.

Thus, there is a need for an antenna for a wireless communication device, in particular a wireless access point with an improved filter.

SUMMARY

It is an objective of the present disclosure to provide an antenna for a wireless communication device, in particular a wireless access point with an improved filter.

The foregoing and other objectives are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect an antenna for a wireless communication device, in particular a wireless access point is provided. The antenna comprises at least one radiating antenna element configured to radiate electromagnetic radiation in response to an electrical input signal, wherein the electrical input signal extends over an operating frequency band. The antenna further comprises a feeding network configured to feed the electrical input signal from an input port of the feeding network to the at least one radiating element for driving the at least one radiating element with the electrical input signal to radiate electromagnetic radiation. Moreover, the antenna comprises a narrowband band-stop filter (sometimes also referred to as a notch filter) configured to filter, i.e. reject a portion of the operating frequency band of the electrical input signal. The narrowband band-stop filter comprises at least one conducting line resonator coupled to the feeding network. The conducting line resonator is configured to filter the input signal in at least one stopband, i.e. a defined portion of the operating frequency band and has a length that is an integer multiple of the quarter wavelength of a stopband frequency, wherein the integer multiple is equal to or larger than 5, for instance, 5, 6, 7, 8, 9, 10 and the like.

Thus, the antenna according to the first aspect provides a low-cost, yet efficient filter with a compact form-factor and a steep-slope band rejection that advantageously may be deployed in in wireless communication device, in particular a wireless AP for providing several radios.

In a further possible implementation form of the first aspect, one coupling end of the conducting line resonator of the narrowband band-stop filter is galvanically or inductively coupled to the feeding network.

In a further possible implementation form of the first aspect, a further end of the conducting line resonator of the narrowband band-stop filter opposite the coupling end is open, wherein the integer multiple is even, for instance, 6, 8, 10 and the like.

In a further possible implementation form of the first aspect, the further end of the conducting line resonator of the narrowband band-stop filter opposite the coupling end is shortened and wherein the integer multiple is odd, for instance, 5, 7, 9 and the like.

In a further possible implementation form of the first aspect, the stopband frequency is a central frequency of the stopband.

In a further possible implementation form of the first aspect, the operating frequency band of the input signal is the 5.15 to 5.85 frequency band and the stopband of the band-stop filter is the 5.15 to 5.33 GHz frequency band.

In a further possible implementation form of the first aspect, the narrowband band-stop filter comprises at least one further conducting line resonator coupled to the feeding network. The at least one further conducting line resonator is configured to filter the input signal frequency band in at least one further stopband, i.e. portion of the operating frequency band and has a length that is an integer multiple of the quarter wavelength of a further stopband frequency, wherein the integer multiple is equal to or larger than 5.

In a further possible implementation form of the first aspect, the further stopband of the at least one further conducting line resonator at least partially overlaps with the stopband of the conducting line resonator. Alternatively, the further stopband of the at least one further conducting line resonator does not overlap with the stopband of the conducting line resonator.

In a further possible implementation form of the first aspect, the antenna further comprises a broadband filter, for instance, an inter-digital broadband filter, coupled to the feeding network, wherein the broadband filter is configured to filter the input signal in a broadband stopband of the input frequency band with a relatively moderate slope, i.e. with a slope less steep than the narrowband band-stop filter.

In a further possible implementation form of the first aspect, the at least one radiating element comprises a dipole antenna element, a slot antenna element, and/or a patch antenna element.

In a further possible implementation form of the first aspect, the conducting line resonator comprises a meander shaped portion, a square spiral shaped portion, a circle spiral shaped portion.

In a further possible implementation form of the first aspect, the antenna further comprises an electrically non-conductive substrate and wherein the conducting line resonator is a micro-strip or strip-line or a co-planar waveguide, i.e. a printed transmission line on the substrate.

According to a second aspect a wireless communication device is provided comprising one or more antennas according to the first aspect.

In a further possible implementation form of the second aspect, the wireless communication device is a Wi-Fi access point or base station.

Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which:

Fig. 1 is a plan view of a filtered monopole antenna according to an embodiment;

Fig. 2 is a table illustrating the performance of the filtered monopole antenna of figure 1 and of a non-filtered monopole antenna;

Fig. 3 is a perspective view illustrating the filtered monopole antenna of figure 1 and a conventional wide monopole antenna placed together;

Fig. 4 is a cooperative table illustrating the performance of the antennas of figure 3 in comparison with the same configuration with 2 conventional wide monopole antennas;

Fig. 5a is a perspective view of a horizontally polarized dipole array antenna according to an embodiment;

Fig. 5b is a detailed view of a central portion of the horizontally polarized dipole array antenna of figure 5a;

Fig. 6 is a comparative table illustrating the performance of the inter-digital filter of the horizontally polarized dipole array antenna of figures 5a and 5b with and without the long conducting line resonators;

Fig. 7 is a detailed view of a portion of an antenna according to a further embodiment; and

Fig. 8 is a schematic diagram of a dipole array antenna according to a further embodiment.

In the following identical reference signs refer to identical or at least functionally equivalent features.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the present disclosure or specific aspects in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps) , even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units) , even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless specifically noted otherwise.

Figure 1 shows a plan view of an embodiment of an antenna 100 for a wireless communication device, such as a Wi-Fi access point (sometimes also referred to as base station) . In the embodiment shown in figure 1, the antenna 100 is, by way of example, a monopole antenna. Thus, the antenna 100 comprises a monopole radiating element 110a that is configured to radiate electromagnetic radiation, such as a RF signal, in response to an input signal, wherein the input signal extends over an operating frequency band. In further embodiments, the antenna 100 may comprise, for instance, a dipole antenna radiating element, a slot antenna radiating element, and/or a patch antenna radiating element.

The antenna 100 further comprises a feeding network 120 that may comprise one or more feeding lines and is configured to feed the input signal from an input port of the feeding network 120 to the monopole radiating element 110a for driving the monopole radiating element 110a with the input signal for causing the monopole radiating element 110a to radiate electromagnetic radiation, such as a RF signal to be received by a wireless station.

Moreover, the antenna 100 comprises a narrowband band-stop filter configured to filter the input signal. To this end, the narrowband band-stop filter comprises a conducting line resonator 140a coupled to the feeding network 120. The conducting line resonator 140a is configured to filter the input signal in at least one stopband of the operating frequency band. In an embodiment, the operating frequency band of the input signal may be the 5.15 to 5.85 WiFi frequency band and the stopband of the band-stop filter may be the 5.15 to 5.33 GHz frequency band. In the embodiment shown in figure 1, the radiating element 110a, the feeding network 120 and the conducting line resonator 140a are provided on an electrically non-conductive substrate 160, e.g. a plastic substrate 160. In an embodiment, the conducting line resonator 140a may be a micro-strip or strip-line or a co-planar waveguide on the plastic substrate 160.

As can be taken from figure 1, the conducting line resonator 140a extends from a coupling end 141a, where the conducting line resonator 140a is galvanically connected or coupled (an inductive coupling may be implemented in a further embodiment) to the feeding network 120, to a further end 142a of the conducting line resonator 140a that in the embodiment shown in figure 1 is open. In another embodiment, the further end 142a of the conducting line resonator 140a may be shortened to the ground. In the embodiment shown in figure 1, the conducting line resonator 140a has a meander like shape, i.e. the conducting line resonator 140a makes from its coupling end 141 to its open end 142a a plurality of turns. Instead or in addition to a meander shaped portion the conducting line resonator 140a may comprise, for instance, a square spiral shaped portion, a circle spiral shaped portion and the like.

In an embodiment, the shape of the conducting line resonator 140a is chosen to maximize the length within the available space for the conducting line resonator 140a on the substrate 160. The length of the conducting line resonator 140a is an integer multiple of the quarter wavelength of a stopband frequency, wherein the integer multiple is equal to or larger than 5 times the quarter wavelength of the stopband frequency. In an embodiment, the stopband frequency is defined by central frequency of the stopband.

In an embodiment, where the further end 142a of the conducting line resonator 140 of the narrowband band-stop filter opposite the coupling end 141a is open, the length of the conducting line resonator 140 is an even integer multiple of the quarter wavelength of the stopband frequency that is larger than 5, for instance, 6, 8 or 10 times the quarter wavelength of the stopband frequency.

In an embodiment, where the further end 142a of the conducting line resonator 140 of the narrowband band-stop filter opposite the coupling end 141a is shortened to the ground, the length of the conducting line resonator 140 is an odd integer multiple of the quarter wavelength of the stopband frequency that is equal to or larger than 5, for instance, 5, 7 or 9 times the quarter wavelength of the stopband frequency.

Figure 2 is a table illustrating the performance of the filtered monopole antenna of figure 1, in comparison with a non-filtered monopole antenna. More specifically, the table of figure 2 shows the S11 value without and with the narrowband band-stop filter 130, the gain, the average gain at an angle of 60 degrees and the roundness at this angle for different frequencies within the frequency range 5.15 GHz to 7.1 GHz. As can be taken from the table of figure 2, the filtered monopole according to an embodiment is not matched in the rejected 5.15-5.33 GHz band. Therefore, most of the input signal (energy) in the rejected band is returned to the signal source and does not enter into the antenna port and therefore does not radiate. Hence, the gain of the monopole in the rejected band is poor. The deteriorated radiation occurs only in the rejected band. In the rest of the band the matching, gain and roundness are good.

Figure 3 is a perspective view illustrating the filtered monopole antenna 100 of figure 1 in comparison with a conventional wide monopole antenna 300 without the conducting line resonator 140 of the antenna 100. Figure 4 is a table illustrating the performance of the antennas 100, 300 of figure 3. More specifically, the table of figure 4 shows the S21 value for the antenna 300 and the antenna 100 as well the additional isolation/loss for for different frequencies within the frequency range 5.15 GHz to 7.1 GHz. As can be taken from the table of figure 4, once 2 wide-band antennas are placed one in front of the other the coupling between them is strong (i.e. poor isolation) , but when one of those antennas is replaced by a filtered antenna according to an embodiment the isolation, in the rejected band, is strongly increased thus enabling the co-existence of 2 radios within the same AP.

Figure 5a is a perspective view of a further embodiment of the antenna 100 in the form of a dipole array antenna 100. Figure 5b is a detailed view of a central portion B of the dipole array antenna 100 of figure 5a. As can be taken from figures 5a and 5b, in this embodiment, the antenna comprises four radially distributed dipole antenna radiating elements 110a-d that are connected via the feeding network 120 to an input port of the feeding network 120. In the embodiment shown in figures 5a and 5b, the comprises narrowband band-stop filter two conducting

line resonators

140a, 140b. The respective coupling end point 141a, b of these two conducting

line resonators

140a, 140b is galvanically connected to a broadband filter 150, in particular an inter-digital filter 150 and thereby coupled to the feeding network 120.

As already described above, the dipole array antenna 100 illustrated in figures 5a and 5b may be part of a WiFi access point. Such a Wi-Fi access point may include in addition to the antenna 100 a housing for housing the antenna 100 as well as electronic components for controlling the antenna 100. In an embodiment, such a Wi-Fi access point may be configured to be mounted on the ceiling of a room in order to communicate with Wi-Fi stations within the room, i.e. underneath the Wi-Fi access point.

In an embodiment, the further conducting line resonator 140b of the dipole array antenna 100 illustrated in figures 5a and 5b may be configured to filter the input signal frequency band in one further stopband of the operating frequency band. Like the conducting line resonator 140a, the conducting line resonator 140b has a length that is an integer multiple of the quarter wavelength of a further stopband frequency, wherein the integer multiple is equal to or larger than 5. In an embodiment, the further stopband of the further conducting line resonator 140b may at least partially overlap with the stopband of the conducting line resonator 140a. Alternatively, the further stopband of the further conducting line resonator 140b does not overlap with the stopband of the conducting line resonator 140a. The broadband filter 150 is configured to filter the input signal in a broadband stopband of the input frequency band with a relatively moderate slope, i.e. with a slope less steep than the narrowband band-stop filter 130 with its two

conducting line resonators

140a, 140b.

Figure 6 is a table illustrating the performance of the filer part of the antenna of figures 5a and 5b. More specifically, the table of figure 6 shows the S11 value and the S21 value at different frequencies for the filter part of the dipole array antenna 100 operated only with the inter digital filter 150 and with the narrowband filter with the conducting line resonators 140a, b. As can be taken from the table shown in figure 6, the slope of the band-pass inter-digital filter 150 in frequency is moderate both in matching (S11) and coupling (filtering) (S21) , while the addition of the conducting line resonators 140a, b highly improves the slope between 5.15 to 5.33 GHz with respect to both aspects (S11, S21) .

Figure 7 is a detailed view of a portion of the antenna 100 according to a further embodiment. In the embodiment shown in figure 7, the conducting line resonator 140a that is galvanically or inductively coupled to the feeding network 120 has the shape of a square-shaped spiral.

Figure 8 is a schematic diagram of the antenna 100 implemented in the form of a dipole array antenna 100 according to a further embodiment. In this embodiment, the narrowband band-stop filter comprises four dipole antenna radiating elements 110a-d as well as four conducting line resonators 140a-d, which are coupled to the feeding network 120 close to the respective dipole antenna radiating element 110a-d. As already described above, the lengths of the four conducting line resonators 140a-d may be such that the four conducting line resonators 140a-d filter the input signal provided via the feeding network in the same or different stopbands of the operating frequency band.

The person skilled in the art will understand that the "blocks" ( "units" ) of the various figures (method and apparatus) represent or describe functionalities of embodiments of the present disclosure (rather than necessarily individual "units" in hardware or software) and thus describe equally functions or features of apparatus embodiments as well as method embodiments (unit = step) .

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described embodiment of an apparatus is merely exemplary. For example, the unit division is merely logical function division and may be another division in an actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

In addition, functional units in the embodiments of the invention may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units are integrated into one unit.

Claims

An antenna (100) for a wireless communication device, the antenna (100) comprising:

at least one radiating element (110a-d) configured to radiate electromagnetic radiation in response to an input signal, wherein the input signal extends over an operating frequency band;

a feeding network (120) configured to feed the input signal from an input port of the feeding network (120) to the at least one radiating element for driving the at least one radiating element (110a-d) with the input signal to radiate electromagnetic radiation; and a narrowband band-stop filter configured to filter the input signal, wherein the narrowband band-stop filter comprises a conducting line resonator (140a) coupled to the feeding network (120) , wherein the conducting line resonator (140a) is configured to filter the input signal in at least one stopband of the operating frequency band and has a length that is an integer multiple of the quarter wavelength of a stopband frequency, wherein the integer multiple is equal to or larger than 5.
The antenna (100) of claim 1, wherein one coupling end (141a) of the conducting line resonator (140a) of the narrowband band-stop filter is galvanically or inductively coupled to the feeding network (120) .
The antenna (100) of claim 2, wherein a further end (142a) of the conducting line resonator (140a) of the narrowband band-stop filter opposite the coupling end (141) is open and wherein the integer multiple is even.
The antenna (100) of claim 2, wherein a further end (142a) of the conducting line resonator (140a) of the narrowband band-stop filter opposite the coupling end (141a) is shortened and wherein the integer multiple is odd.
The antenna (100) of any one of the preceding claims, wherein the stopband frequency is a central frequency of the stopband.
The antenna (100) of any one of the preceding claims, wherein the operating frequency band of the input signal is the 5.15 to 5.85 frequency band and the stopband of the narrowband band-stop filter is the 5.15 to 5.33 GHz frequency band.
The antenna (100) of any one of the preceding claims, wherein the narrowband band-stop filter comprises at least one further conducting line resonator (140b-d) coupled to the feeding network (120) , wherein the at least one further conducting line resonator (140b-d) is configured to filter the input signal frequency band in at least one further stopband of the operating frequency band and has a length that is an integer multiple of the quarter wavelength of a further stopband frequency, wherein the integer multiple is equal to or larger than 5.
The antenna (100) of claim 7, wherein the further stopband of the at least one further conducting line resonator (140b-d) at least partially overlaps with the stopband of the conducting line resonator (140b-d) or wherein the further stopband of the at least one further conducting line resonator (140b-d) does not overlap with the stopband of the conducting line resonator (140a) .
The antenna (100) of any one of the preceding claims, wherein the antenna (100) further comprises a broadband filter (150) coupled to the feeding network (120) , wherein the broadband filter (150) is configured to filter the input signal in a broadband stopband of the input frequency band.
The antenna (100) of any one of the preceding claims, wherein the at least one radiating element (110a-d) comprises a dipole antenna element, a slot antenna element, and/or a patch antenna element.
The antenna (100) of any one of the preceding claims, wherein the conducting line resonator (140a) comprises a meander shaped portion, a square spiral shaped portion, a circle spiral shaped portion
The antenna (100) of any one of the preceding claims, wherein the antenna (100) further comprises an electrically non-conductive substrate (160) and wherein the conducting line resonator (140a) is a micro-strip or strip-line or a co-planar waveguide on the substrate (160) .
A wireless access point comprising one or more antennas (100) according to any one of the preceding claims.